Method of swaging interrupted threads in a sheet metal nut



Oct. 31, 1961 F. E. JOHNSON, JR 3,006,003

METHOD OF SWAGING INTERRUPTED THREADS IN A SHEET METAL NUT Filed April 15, 1959 Maui: E. Jofinsou Jr,

fwvewiorl United States Patent 3,006,003 METHOD OF SWAGING INTERRUPTED THREADS IN A SHEET METAL NUT Frank E. Johnson, Jr., Malden, Mass., assignor to United- Carr Fastener Corporation, Cambridge, Mass., a corporation of Delaware Filed Apr. 15, 1959, Ser. No. 806,481 2 Claims. (Cl. 10-86) My invention relates to the method of forming threads on a nut, particularly in the inside wall of a nut to receive a threaded bolt.

An object of my invention is to provide an improved method of forming nut threads so as to eliminate a costly secondary threading operation as presently used in threading nuts.

A further object of my invention is to form a sheet metal nut with a barrel portion and then form threads therein in the same tools and machine as forms the barrel of the nut and Without using a rotary threading tool, but by a simple mandrel having opposed threaded sides and other opposed unthreaded sides. The mandrel cooperates with squeezing or swaging dies and the mandrel may be moved out of the barrel of the nut, after the threads are formed, by a simple 90 turn and a nonrotating axial withdrawal.

Thus my invention provides for a simple, fast and cheap method of forming threads in a nut.

Other objects of the invention will, in part, be obvious, and will, in part, appear hereinafter.

In the drawing which illustrates a preferred form of my invention:

FIG. 1 is an edge view of a strip showing some of the steps taken to form my invention;

FIG. 2 is a section taken on the line 2-2 of FIG. 1 with the thread forming mandrel in elevation and the swaging dies added and in swaging position;

FIG. 3 is a view similar to FIG. 2 with the mandrel rotated to a position for retraction and the swaging dies released;

FIG. 4 is an enlarged plan section taken on the line 4-4 of FIG. 2 with part of the tool die block added in section;

FIG. 5 is an enlarged section taken on the line 5-5 of FIG. 4 and also showing a part of the tool die block in section;

FIG. 6 is a side view of a bolt and closed end nut made according to my improved method;

FIG. 7 is a section of the nut shown in FIG. 6 with out the bolt; and

FIG. 8 is a side view of a bolt and nut, the nut having an open end in the barrel.

Referring first to the preferred forms of nuts made by my improved method, I have shown a sheet metal nut having a base flange 1, a barrel 2, an inside wall 3, and cooperating threads formed in groups opposite each other as best illustrated in FIGS. 3 and 7. Thus the threads are not continuous around the wall 3, the reasons for which will be described later.

The nut shown in FIGS. 6 and 7 has a closed bottom wall 5, while the bottom wall is punched out in the nut shown in FIG. 8 so that the shank of a bolt 6 may pass through the barrel of the nut as illustrated.

Sheet metal threaded nuts are well known in the art and have been made by, first, manufacturing the nut with an unthreaded barrel in a conventional type of metal working press, then the nuts have been threaded in various types of thread tapping machines. This method of making the nuts requires additional handling of the parts, expensive tapping equipment and a relatively slow operation. Applicant has found that the nuts can be threaded in the conventional press by using a mandrel 7 at a station in the press after the final cup or barrel shape has been formed as shown in FIG. 1. This mandrel 7 is moved into and out of the barrel as the forming tools in the machine are moved toward and away from each other. By incorporating squeezing or swaging dies 8-8 at the station where the mandrel is inserted and moving these swaging dies toward and away from each other, I squeeze opposite sides of the barrel against oppositely threaded portions 9-9 of the mandrel 7 as shown in FIG. 2. After the threads have been formed the mandrel is rotated as shown in FIG. 3 so that the flat unthreaded sides 10-10 of the mandrel are opposite the threads in the barrel in the nut. Since the distance between the flat sides 10-10 is less than the distance between the threaded sides 9-9 of the mandrel, the mandrel may be moved axially out of the nut when the parts of the die blocks are moved away from each other. The type of press applicant has in mind, the use of slidable swaging dies 8-8, the mechanism for operating those dies (not shown) and the mechanism for rotating the mandrel 90 (also not shown) will be well understood by anyone skilled in the art and therefore, it is not necessary to illustrate such mechanisms.

In FIG. 4 I have shown, in more detail, how the swaging dies 8-8 press opposite sides of the barrel 2 against the threaded sides 9-9 of the mandrel and part of the tool die block 11 is shown in this illustration. In FIG. 5 I have shown, more in detail, the retracted positions of the swaging dies and the rotated position of the mandrel to illustrate that the mandrel may now be free axially, and without rotation, withdrawn from the barrel of the nut. Thus it Will be seen that for very little cost of tooling and for almost no extra operating time, the nut can be completely formed and threaded in a conventional press.

While the threads in my nut, formed by my improved method, are not continuous around the inside of the barrel, I have found that for most nut and bolt applications that the opposed segments cooperate with the thread on a bolt and have enough interengagement holding power for the average bolt application.

While I have illustrated a preferred novel method of forming threads in a nut, my invention is best described by the following claims.

I claim:

1. The method of forming partial threads on the inside wall only of a nut which comprises inserting, into an aperture in said nut surrounded by said wall, a mandrel having threads at opposite sides and having unthreaded opposite sides a shorter distance apart than the threaded sides and at right angles to the threaded sides, squeezing the inside wall of the nut against the threaded sides of the mandrel by the use of opposed unthreaded swaging dies to flatter portions of the wall of the nut and form partial threads in the inner surface only of said wall, rotating one of said nut and mandrel relative to the other to bring the unthreaded sides of the mandrel opposite the threaded portions in the wall and then moving one axially relative to the other free of any rotating motion, thereby to remove the nut from the mandrel.

2. The method of forming threads on the inside Wall of a sheet metal nut, in the same machine as forms the nut, which first comprises drawing a sheet metal blank into a cup shaped portion having a barrel with an inside wall to be threaded, then inserting into an aperture in said nut surrounded by said wall, a mandrel having threads at opposite sides and having unthreaded opposite sides a shorter distance apart than the threaded sides and at right angles to the threaded sides, squeezing the inside wall of the nut against the threaded sides of the mandrel Patented Oct. 31, 1961 by tliemsa of apposed swaging dies to form partial threads References Cited in'the file of this patent insaid wall, rotating one of said nut and mandre1 rela: 4 t i tive to the other to bring the unthreaded sides of the UNITED STATES PATENTS mandrel opposite the threaded portions in the wall and 856,316 Thurston June 11, 1907 thenkmoying eneraxially relatiyeto'the other free of. ny 5 1,2 1,014 Dorgan A r. 2, 1918 mutating. motion thereby to remove the nut from the 1949 923 Unke Man 6 1934 mandrel. i i n'nu' 

